The present invention relates to custom motorcycles and in particular to apparatus for adjusting the rake and trail of motorcycle forks.
Custom motorcycle riders and builders often extend the fork angle (or rake) to obtain a desired look or a desired motorcycle feel. Various methods may be employed to extend the fork angle, ranging from permanent modifications to the motorcycle frame by modifying the angle of the steering head, to an adjustable bolt-on kit.
Most rake extension kits retain the original axis of rotation of the forks and angularly offset the forks with respect to the steering head of the frame. Such kits are disclosed in U.S. Pat. No. 5,967,538 for “ADJUSTABLE MOTORCYCLE TRIPLE TREE” and U.S. Pat. No. 4,565,384 for “MOTORCYCLE FORK TREE.” While these kits allow adjustment of the fork rake, they also undesirably alter the trail (see FIG. 3A.) Such alteration of the trail often results in a less desirable and potentially unsafe motorcycle feel and/or handling.
Another rake adjustment kit is described in U.S. Pat. No. 3,866,946 for “MOTORCYCLE STEERING HEAD ANGLE ADJUSTMENT.” The kit disclosed in the '946 patent includes eccentrics in the steering head to adjust the fork rake, and as a result is severely limited in the amount of adjustment.